Annual grasses and large broadleafed weeds have hindered the growing of corn, sugar beets, sorghum, sugar cane, macadamia orchards and pineapples. Cultivation of crops, which heretofore was the most widely used method of eliminating weeds, has given way more recently to the use of pre-emergence and postemergence selective herbicides.
Pre-emergence selective herbicides are applied directly to the soil during or just prior to the planting season. Postemergence selective herbicides are applied to the fields after the weeds have begun to grow and preferably before they have reached the height of six inches or more. Weeds which most seriously plague farmers include lambsquarters (Chenopodium album), ragweed (Ambrosia artemisiifolia), barnyard grass (Echinochloa crusgalli), smartweed (Polygonum pennsylvanicum), velvet leaf (Abutilon theophrasti), quackgrass (Agropyron repens), witchgrass (Panicum capillare), redroot pigweed (Amoranthus retroflexus), yellow foxtail (Setaria glauca), giant foxtail (Setaria faberi), large crabgrass (Digitaria sanguinalis), fall panicum (Panicum dichotomiflorum), yellow nutsedge (Cyperus esculentus) and others.
Many of these weeds present a real problem to farmers because they often reinvade the fields in midsummer usually after pre-emergence herbicides are no longer effective. Postemergence herbicides are now normally required to sustain production of crops when the midsummer invasion of weeds occur.
Compounds such as substituted diamino, chloro triazines, chlorinated organic acids and their salts and esters, as well as many organo, phosphor and sulfur compounds have been demonstrated to be effective postemergence selective herbicides for combating undesired plant growth of the species of weeds hereinabove disclosed.
Of these herbicides one of the most widely used is the substituted diamino,chloro-S-triazines. This class of compounds can be generally defined by the structural formula ##STR1## wherein R.sub.1 R.sub.2 R.sub.3 and R.sub.4 can each be selected from the group consisting of the hydrogen and alkyl, cycloalkyl alkenyl, hydroxyalkyl, arathyl radicals. Compounds of the type herein defined are disclosed in U.S. Pat. No. 2,891,855 issued June 23, 1959. Some of the compounds defined include:
2-chloro-4-ethylamino-6-isopropylamino-5-triazine PA1 2-chloro-4-amino-6-ethylamino-5-triazine PA1 2-chloro-4-amino-6-n-propylamino-5-triazine PA1 2-chloro-4-amino-6-n-butylamino-5-triazine PA1 2-chloro-4-amino-6-alkylamino-5-triazine PA1 2-chloro-4-amino-6-diethylamino-5-triazine PA1 2-chloro-4-methylamino-6-ethylamino-5-triazine PA1 2-chloro-4-methylamino-6-n-propylamino-5-triazine PA1 2-chloro-4,6-bis-ethylamino-5-triazine PA1 2-chloro-4-ethylamino-6-propylamino-5-triazine PA1 2-chloro-4-ethylamino-6-(.beta.-hydroxy-ethylamino)-5-triazine PA1 2-chloro-4-ethylamino-6-diethylamino-5-triazine PA1 2-chloro-4,6-bis-diethylamino-5triazine
and others. Herbicidal compounds such as 2,4-dichloropropionic acid and 2,4-dichlorophenoxyacetic acid are also included among the postemergence organic herbicides known to the art. Many of these well known selective herbicides are also disclosed in "Herbicide Handbook of the Weed Society of America," First Ed. 1967, W. F. Humphrey Press Inc., Geneva, N.Y.
Recently it has been disclosed that petroleum hydrocarbon spray oils in aqueous emulsion form provide carriers which enhance the effectiveness of certain herbicides. It has also been disclosed that certain emulsifying agents as well as vegetable oil or crop oil emulsions also effectively enhance the weed killing function of the herbicide when combined with these carriers. For example, it was reported by John D. Naleweja in an abstract published in "Proceedings North Central Weed Control Conference", (December, 1968, Indianapolis, Ind.), page 12 that sunflower oil-in-water emulsions and linseed oil-in-water emulsions were as effective as petroleum hydrocarbon oil-in-water emulsions when used as carriers for 2-chloro-4-ethylamino-6-isopropylamino-S-triazine (atrazine) when used as a postemergence herbicide. The paper discloses that 1 gallon per acre of crop seed oil was as effective as 1 gallon per acre of petroleum hydrocarbon oil as a carrier for atrazine herbicide in combating weed growth. A new herbicide carrier oil composition which substantially enhances the effectiveness of herbicides while requiring much less oil has now been discovered.